This application requests 3 years of funding to support individual post-doctoral training in behavioral, brain stimulation, and neuroimaging techniques. The proposed work will employ state-of-the-art approaches like concurrent TMS-fMRI and noninvasive neuromodulation to investigate crossmodal recruitment of sensory brain areas in healthy humans. Studies with blind and deaf individuals indicate that visual cortex (VC) and auditory cortex (AC) can respond to tactile stimulation alone. This activity is thought to reflect large-scale changes in brain organization resulting from sensory deprivation. There is considerably less evidence for crossmodal recruitment of unisensory areas in typically developing brains - in some instances, tactile stimulation can evoke neural activity in VC and AC, but the behavioral significance of this activity is unclear. Crossmodal recruitment of unisensory areas in typically developing brains challenges prevailing, hierarchical models of cortical organization. Correctly interpreting crossmodal recruitment is critically important for a more complete understanding of sensory processing and may inform novel rehabilitation interventions for treating sensory deficits. This proposal's main objective is to characterize the interactions between somatosensory cortex (SC) and VC and AC during tactile stimulus perception. Anodal tDCS will be used to address Specific Aim 1: the contributions of VC and AC to tactile shape and frequency perception will be revealed in psychophysical experiments. Subjects' tactile spatial acuity and frequency sensitivity will be assessed before, during, and after enhancement of VC and AC excitability with anodal tDCS. Improved tactile thresholds resulting from VC and AC modulation will indicate these areas' roles in tactile orientation and frequency perception. Concurrent TMS- fMRI will be used to address Specific Aim 2: simultaneous whole brain imaging and focal stimulation of SC while subjects discriminate tactile stimulus features will directly reveal attention-modulated connectivity between SC and cortical networks involved in tactile orientation and frequency perception. Stimulation of SC will evoke BOLD activations in VC and AC if these areas are recruited and functionally linked during the perception of tactile stimulus orientation and temporal frequency, respectively. The results of these experiments will further our understanding of sensory processing and brain organization. Successful completion of this training plan will also solidify the Applicant's expertise in a wide variety of separate and combined research methods, which will enable him to become a successful independent researcher.